1 /*
2 * This module determines the type of socket (datagram, stream), the client
3 * socket address and port, the server socket address and port. In addition,
4 * it provides methods to map a transport address to a printable host name
5 * or address. Socket address information results are in static memory.
6 *
7 * The result from the hostname lookup method is STRING_PARANOID when a host
8 * pretends to have someone elses name, or when a host name is available but
9 * could not be verified.
10 *
11 * When lookup or conversion fails the result is set to STRING_UNKNOWN.
12 *
13 * Diagnostics are reported through syslog(3).
14 *
15 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
16 */
17
18#ifndef lint
19static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24";
20#endif
21
22/* System libraries. */
23
24#include <sys/types.h>
25#include <sys/param.h>
26#include <sys/socket.h>
27#include <netinet/in.h>
28#include <netdb.h>
29#include <stdio.h>
30#include <syslog.h>
31#include <string.h>
32
33extern char *inet_ntoa();
34
35/* Local stuff. */
36
37#include "tcpd.h"
38
39/* Forward declarations. */
40
41static void sock_sink();
42
43#ifdef APPEND_DOT
44
45 /*
46 * Speed up DNS lookups by terminating the host name with a dot. Should be
47 * done with care. The speedup can give problems with lookups from sources
48 * that lack DNS-style trailing dot magic, such as local files or NIS maps.
49 */
50
51static struct hostent *gethostbyname_dot(name)
52char *name;
53{
54 char dot_name[MAXHOSTNAMELEN + 1];
55
56 /*
57 * Don't append dots to unqualified names. Such names are likely to come
58 * from local hosts files or from NIS.
59 */
60
61 if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) {
62 return (gethostbyname(name));
63 } else {
64 sprintf(dot_name, "%s.", name);
65 return (gethostbyname(dot_name));
66 }
67}
68
69#define gethostbyname gethostbyname_dot
70#endif
71
72/* sock_host - look up endpoint addresses and install conversion methods */
73
74void sock_host(request)
75struct request_info *request;
76{
77 static struct sockaddr_in client;
78 static struct sockaddr_in server;
79 int len;
80 char buf[BUFSIZ];
81 int fd = request->fd;
82
83 sock_methods(request);
84
85 /*
86 * Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov>
87 * suggested how to get the client host info in case of UDP connections:
88 * peek at the first message without actually looking at its contents. We
89 * really should verify that client.sin_family gets the value AF_INET,
90 * but this program has already caused too much grief on systems with
91 * broken library code.
92 */
93
94 len = sizeof(client);
95 if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) {
96 request->sink = sock_sink;
97 len = sizeof(client);
98 if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
99 (struct sockaddr *) & client, &len) < 0) {
100 tcpd_warn("can't get client address: %m");
101 return; /* give up */
102 }
103#ifdef really_paranoid
104 memset(buf, 0 sizeof(buf));
105#endif
106 }
107 request->client->sin = &client;
108
109 /*
110 * Determine the server binding. This is used for client username
111 * lookups, and for access control rules that trigger on the server
112 * address or name.
113 */
114
115 len = sizeof(server);
116 if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
117 tcpd_warn("getsockname: %m");
118 return;
119 }
120 request->server->sin = &server;
121}
122
123/* sock_hostaddr - map endpoint address to printable form */
124
125void sock_hostaddr(host)
126struct host_info *host;
127{
128 struct sockaddr_in *sin = host->sin;
129
130 if (sin != 0)
131 STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr));
132}
133
134/* sock_hostname - map endpoint address to host name */
135
136void sock_hostname(host)
137struct host_info *host;
138{
139 struct sockaddr_in *sin = host->sin;
140 struct hostent *hp;
141 int i;
142
143 /*
144 * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does
145 * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does
146 * not work the other way around: gethostbyname("INADDR_ANY") fails. We
147 * have to special-case 0.0.0.0, in order to avoid false alerts from the
148 * host name/address checking code below.
149 */
150 if (sin != 0 && sin->sin_addr.s_addr != 0
151 && (hp = gethostbyaddr((char *) &(sin->sin_addr),
152 sizeof(sin->sin_addr), AF_INET)) != 0) {
153
154 STRN_CPY(host->name, hp->h_name, sizeof(host->name));
155
156 /*
157 * Verify that the address is a member of the address list returned
158 * by gethostbyname(hostname).
159 *
160 * Verify also that gethostbyaddr() and gethostbyname() return the same
161 * hostname, or rshd and rlogind may still end up being spoofed.
162 *
163 * On some sites, gethostbyname("localhost") returns "localhost.domain".
164 * This is a DNS artefact. We treat it as a special case. When we
165 * can't believe the address list from gethostbyname("localhost")
166 * we're in big trouble anyway.
167 */
168
169 if ((hp = gethostbyname(host->name)) == 0) {
170
171 /*
172 * Unable to verify that the host name matches the address. This
173 * may be a transient problem or a botched name server setup.
174 */
175
176 tcpd_warn("can't verify hostname: gethostbyname(%s) failed",
177 host->name);
178
179 } else if (STR_NE(host->name, hp->h_name)
180 && STR_NE(host->name, "localhost")) {
181
182 /*
183 * The gethostbyaddr() and gethostbyname() calls did not return
184 * the same hostname. This could be a nameserver configuration
185 * problem. It could also be that someone is trying to spoof us.
186 */
187
188 tcpd_warn("host name/name mismatch: %s != %.*s",
189 host->name, STRING_LENGTH, hp->h_name);
190
191 } else {
192
193 /*
194 * The address should be a member of the address list returned by
195 * gethostbyname(). We should first verify that the h_addrtype
196 * field is AF_INET, but this program has already caused too much
197 * grief on systems with broken library code.
198 */
199
200 for (i = 0; hp->h_addr_list[i]; i++) {
201 if (memcmp(hp->h_addr_list[i],
202 (char *) &sin->sin_addr,
203 sizeof(sin->sin_addr)) == 0)
204 return; /* name is good, keep it */
205 }
206
207 /*
208 * The host name does not map to the initial address. Perhaps
209 * someone has messed up. Perhaps someone compromised a name
210 * server.
211 */
212
213 tcpd_warn("host name/address mismatch: %s != %.*s",
214 inet_ntoa(sin->sin_addr), STRING_LENGTH, hp->h_name);
215 }
216 strcpy(host->name, paranoid); /* name is bad, clobber it */
217 }
218}
219
220/* sock_sink - absorb unreceived IP datagram */
221
222static void sock_sink(fd)
223int fd;
224{
225 char buf[BUFSIZ];
226 struct sockaddr_in sin;
227 int size = sizeof(sin);
228
229 /*
230 * Eat up the not-yet received datagram. Some systems insist on a
231 * non-zero source address argument in the recvfrom() call below.
232 */
233
234 (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size);
235}